Income Taxes (Summary Of Tax Loss And Tax Credit Carryforwards) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Tax Credit Carryforward [Line Items]
Deferred tax asset on tax carryforwards	$ 124.5	$ 120.7
Valuation Allowance, Amount	(153.4)	$ (150.0)
Tax Loss and Credit Carryforwards [Member]
Tax Credit Carryforward [Line Items]
Deferred tax asset on tax carryforwards	124.5
Valuation Allowance, Amount	(118.3)
Net deferred tax asset on tax carryforwards	6.2
U.S. Federal Tax Credits [Member]
Tax Credit Carryforward [Line Items]
2020-2024	2.8
After 2024	4.6
Indefinite	0.0
Total tax carryforwards	7.4
Deferred tax asset on tax carryforwards	7.4
Valuation Allowance, Amount	(6.5)
Net deferred tax asset on tax carryforwards	0.9
U.S Federal Tax Losses [Member]
Tax Credit Carryforward [Line Items]
2020-2024	0.0
After 2024	0.8
Indefinite	0.0
Total tax carryforwards	0.8
Deferred tax asset on tax carryforwards	0.2
Valuation Allowance, Amount	(0.2)
Net deferred tax asset on tax carryforwards	0.0
U.S. State Tax Credits [Member]
Tax Credit Carryforward [Line Items]
2020-2024	3.3
After 2024	2.4
Indefinite	22.8
Total tax carryforwards	28.5
Deferred tax asset on tax carryforwards	22.6
Valuation Allowance, Amount	(21.0)
Net deferred tax asset on tax carryforwards	1.6
U.S. State Tax Losses [Member]
Tax Credit Carryforward [Line Items]
2020-2024	97.8
After 2024	797.2
Indefinite	7.2
Total tax carryforwards	902.2
Deferred tax asset on tax carryforwards	45.0
Valuation Allowance, Amount	(43.0)
Net deferred tax asset on tax carryforwards	2.0
Non-U.S. Tax Losses [Member]
Tax Credit Carryforward [Line Items]
2020-2024	12.4
After 2024	7.4
Indefinite	215.6
Total tax carryforwards	235.4
Deferred tax asset on tax carryforwards	49.3
Valuation Allowance, Amount	(47.6)
Net deferred tax asset on tax carryforwards	$ 1.7